1. Field of the Invention
The present invention relates to digital image processing and, more particularly, to processing digital images using multiple spatial channels.
2. Description of the Related Art
It is possible to develop devices such as printers or displays that have the capacity to produce larger, lower density dots, in addition to the usual variety. Researchers have recently been developing printers that can produce dots with more than one spatial distribution of colorant. One example that is now in common use is a printer that can produce very small dots in addition to dots of the usual size, allowing resolution enhancement (RET). A new alternative is a printer that can produce dots that are larger than the usual size. For example, an experimental ink-jet pen has been developed that can produce two types of dots: small strongly pigmented dots and large dilutely pigmented dots. Researchers have created this device with the hope of reducing the visibility of the halftone pattern in bright image regions. Until now, however, there has been no method that successfully utilizes the new capacity to achieve this desired effect. A simple substitution of the large dilute dots for the small concentrated dots in the highlight areas introduces contouring, and only serves to reduce image quality.
Thus, it can be seen that single dot size image processing techniques impose output quality limits upon current multiple dot sized devices, and hinder the use of these devices in many applications.
Therefore, there is an unresolved need for a technique that can produce near continuous-tone output quality from a multiple dot size device by overcoming contouring artifacts and thereby producing vastly improved images over techniques that use only a single dot type.